1. Field of the Invention
The present invention relates to a cellular phone having a navigation device, correction value initialization method, and navigation function, and for example can be favorably applied to a navigation device that can detect an azimuth with a geomagnetism sensor.
2. Description of the Related Art
Hitherto, navigation devices have been widely used which are mounted on vehicles or the like that move, calculate the current position based on a GPS (Global Positioning System) signal transmitted from a GPS satellite, and indicate the position of the vehicle and direction for advancing on a map screen.
Also, there are navigation devices called a PND (Personal Navigation Device) which a user can readily carry between a vehicle and a home or the like, or between vehicles, and which can perform map screen displays or the like even when being carried.
Of these PNDs, a PND has been proposed which has a geomagnetism sensor that detects geomagnetism implemented therein, calculates orientation based on the detection results of the detected geomagnetism, and displays a map screen that matches the orientation (e.g., see Japanese Unexamined Patent Application Publication No. 2008-076374).
Besides a PND, portable electronic devices such as cellular phones for example have been proposed which have measuring functions, map display functions and the like, and further have a geomagnetism sensor and display a map screen matching the orientation.
Now, geomagnetism sensors are easily influenced by the magnetic field by a magnetic substance such as metal or the like nearby, and further, even in cases wherein the magnetism in a metallic part such as a shield plate or the like provided within the PND changes, there are cases of influence thereof.
Therefore, when starting to compute orientation with a geomagnetism sensor, the PND performs predetermined initialization processing (e.g., correction value adjustments and so forth), whereby the orientation can be appropriate computed based on detection signals obtained from the geomagnetism sensor.
On the other hand, there are PNDs which can shift to a suspended state wherein only a portion of the internal circuits and so forth are operated when a user is temporarily not using and so forth, similar to a general-use computer or the like.
Upon predetermined return operations being performed, a PND that has shifted to a suspended state omits the initialization processing and the like which is performed at time of normal start-up, is restored to the operating state immediately prior to the shift to the suspended state, and can immediately start continuing operations.
However, there are cases wherein, at the time of return operations from the suspended state, the PND has been moved to a location that is different from immediately prior to shifting to the suspended state where surrounding the magnetic field is different, and cases wherein, in the event of being moved in the suspended state, the PND is influenced by the surrounding magnetic field, and magnetism of the internal metallic parts change.
In such cases, there has been the problem that the PND may not correctly detect the orientation by the geomagnetism sensor, and the map screen matching the current orientation may not be correctly displayed.
It has been found desirable to provide a cellular phone having a navigation device that can improve detection accuracy of orientation by a geomagnetism sensor, correction value initialization method, and navigation function.